Alpha-bromoethylpentachloro-benzene



Patented July 8, 1952 ENTj-QFFHCE A ALPHA-BROMOETHYLPENTACHLORO- BENZENE Sidney D. Ross andMoushy Markarian, North Adams, and MathewNazzewski, Adams, Mass., assignors to Sprague Electric Company, NorthAdams, Mass., a corporation of Massachusetts No Drawing.Application'February 10, 1947, Serial No. 727,736

1 Claim.

This invention relates to new halogenated aromatic compounds and moreparticularly refers to bromoethyl pentachlorobenzene and its closelyrelated derivatives.

An object of this invention is' to produce new alkyl substitutedderivatives of polyhalogenated benzene. A further object is to producenew and useful halogenated derivatives of alkyl pentachlorobenzenes. Astill further object is to produce new derivatives ofethylpentachlorobenzene by relatively simple processes. Additionalobjects will become apparent from the following description and claim.

These objects are attained in accordance with our invention whichbroadly is directedto a, class of compounds conforming to the generalformula: 1

(Chew; n

wherein R, isa bromo-alkyl group, and. is an integer from 1 to 5.

In a, more restricteds'e'nse this invention is concerned with compoundsconforming to the general f ormula wherein R is an alkyl group,preferably containingfrom two to four carbon atoms, and :1: is aninteger from l to 5, preferably 1 or 2. i

The following tabulation includes representative compounds embracedwithin the scope of this invention:

beta tribromoethylpentachlorobenzene compound; I

Beta, beta, beta" tribromoethylpentachlorobenzene 1,2dibromo-2-pentachlorophenyl-propane 1,2dibromo-1-pentachlorophenyl-propane- 1,3 dibromo-1-pentachlorophenylpropanel 3 2,3 dibromo-l-pentachlorophenyl-propane 1,3dibromo-2-pentachlorophenyl-propane Pentachlorobenzylbromide= One of thepreferred embodiments of the invention concerns monob'romo derivativesof ethyl pentachlorobenzene, specificallyalphabromoethylpentachlorobenzene and betabromoethylpentachlorobenzene.

We have found that the compounds of this invention may be produced byprocesseswhich are simple and eflicient. The following examples areillustrative of these processes:

EXAMPLE 1 Prcpa'mtion of alphabromo ethylpemtachlorobenzene 2785 gramsof ethylpentachlorobenzene were heated to -100" 0. in a three-neckedflask, fitted with a dropping funnel, reflux condenser and a mechanicalstirrer. A 200 watt unfrosted bulb was placed next to the hash andilluminated during the reaction. 159.8 grams of bromine were addedslowly over a twelve-hour period. Hydrogen bromide was given off duringthe addition. The reaction mixture Was poured into an evaporating dishand evac'uated over potassium,hy-

droxide and calcium chloride. The crudeprodnot thus obtained weighed 325grams and melted at"' 105'-1l5 C. r This represents a 90% yield ofRecrystallization from acetone brought the melting point 'of thealphabromoethylpentachlorobenzene to"1 2 1-12'2 C. A' secondrecrystallization of this material brought the melting point to 123-124I C. Carbon and hydrogen analyses performed upon the pure materialconfirmed the empirical formula.

. EXAMPLE 2 Preparation of alphabromoethylpefitacshlorobenzene I Theprocedure of Example 1 was followed with the exception that thetemperature of the reacting material was maintained at'about1'40 C. andthe time of'addition was. 2fl hours. There was obtained a 68% yield ofthefalpha bromo 3 EXAMPLE 3 Preparation ofralphrabromoethylpentachlorobenzene The procedure of Example 1 wasfollowedwith the exception that the temperature was maintained at 180 C.and the bromine added over a 6-hour period. A substantial yield of thealpha g bromo compound was obtained but the percent-- age was smallerthan in Examples 1 and 2.

EXAMPLE 4 Preparation of alphabromoethylpertta'chlorobenzene 2 grams ofmethyl pentachlorophenyl carbinol,

a known compound prepared by the method of Gunther Lock, Ber. 72B, 1939,pp. 300-304, and

10 grams of 48% hydrobromic acid were refluxed for two hours, with anoil bath temperature of EXAMPLE 5 \betabromoethylpentachloro benzene92.5 grams; (.5 mole) beta phenylethylbromide 2.5 grams AlCla 4.1 gramsS2012 404 grams 802012 The beta phenylethylbromide and aluminum chloridewere placed in a 50 cc. three-necked flask equipped with a refluxcondenser, thermometer and dropping funnel. The sulfur chlo- Preparationof -ride and sulfuryl chloride mixture was run in slowly at roomtemperature. After a short time the, aluminum chloride dissolved andtheevolution of hydrochloric acid began. The color changed to yellow,then brown and the temperature began to go up but was maintained below60 C. by means of an ice bath until approximately one-half of thechlorinating mixture had been added. The temperature was then maintainedat 60-64 C. by means of a heating mantle for the rest of the additionperiod and for one and one-quarter hours thereafter. The reactionmixture was allowed to stand at .room temperature over night and thereaction continued as evidenced by the evolution of hydrochloric acid.The next morning the mixture was melting from 88-95 C. The product wasdissolved in 95% ethanol, with a separation of a small amount of tar andupon cooling crystals were deposited with a melting point of 96-98 C.

Upon recrystallization from a mixture ;of ace- 4 tone and alcohol therewas obtained 84 grams of melting point 96.5-98" C. The mother liquor wasworked up and a total yield of grams of betabromoethylpentachlorobenzenewas obtained... Threerecrystallizations from acetone in alcohol broughtthe melting pointto 98-99 C. A mixed melting point with the material ofExample 1 gave a highly depressed melting point indicating that thesetwo compounds were not the same.'

EXAMPLE 6 Preparation of 1-pentachZorophenyl-1-aceto:cy-

' ethane 17.9 grams of the alphabromoethylpentachlorobenzene produced inExample 1 were refluxed with 19.6 grams of potassium acetate and 275 cc.of acetic acid for 20 hours. At the end of this time most of the aceticacid was removed with a water pump and the residue taken up in benzeneand water. The benzene layer ,was separated and dried and subjected todistillation to remove most of the benzene. The residue was dissolved inacetone and water and the product crystallized therefrom to give amelting point of 90-95 C. Upon three recrystallizations' from methanolthe pure acetoxycompound possessed a melting point of 101 102 'c. V

v EXAMPLE 7 v Preparation of methylpentachlorocarbinol 2 grams of thel-pentachlorophenyl-l-acetoxyethane produced in Example 6 were refluxedfor four hours with 1 gram of potassium hydroxide dissolved in 25 cc. ofwater and cc. of acetone. At the end of this time most of the acetonewas removed with a water pump vacuum and more water then added, giving aprecipitate which when filtered and dried weighed 1.9 grams. Thismaterial possessed a melting point of l20.5-122 C. Uponrecrystallization from methanol and water the melting point was raisedto 124-125'C. A mixed melting point was made with the carbinol producedby Gunther Lock previously referred to, to give a melting point of122-123" 0., indicating that these compounds are identical.

The bromination of ethylpentachlorobenzene is generally conducted in atemperature range from about 60 C. to about 200 0., although lowertemperatures may be employed when a solvent for theethylpentachlorobenzene is employed.

The ring chlorination of beta phenylethylbromide as describedpreviouslyis advisably con- "ducted at'a low temperature to minimize thecondensation reactions which may occur in the presence of aluminumchloride. The temperature is generally at'or below the refluxtemperature of the chlorinating agents. Alternately the chlorination maybe conducted with liquid or gaseous chlorine in the presence of iron.

Pentachlorobenzyl bromide may be prepared by low temperature ringchlorination of benzyl bromide or by bromination of pentachlorotoluene.The compounds of this invention may be used as intermediates in theformation of numerous organic compounds. They possess a very high flashpoint and will not sustain flame per se, and above their melting pointsare good solvents for aromatic and chlorinated compounds. As heattransfer agents they are likewise useful. Because the aliphaticbromine'is quite reactive, it is possible to use the compounds of theinvention in a large number of useful reactions such as theFriedel-Crafts reaction, with aromatic compounds; dehydrohalogenationwith caustic, etc.

As many apparently widely different embodiments of this invention may bemade without departing from the spirit and scope hereof, it is to beunderstood that the invention is not limited to the specific embodimentshereof except as defined in the appended claim.

What we claim is: Alpha-bromoethylpentachlorobenzene, a solid possessinga melting point of 123-124 C.

SIDNEY D. ROSS. MOUSHY MARKARIAN. MATHEW NAZZEWSKI.

6 REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 2,174,513 7 Holt et a1 Oct. 3,1939 2,193,823 Levine et al Mar. 19, 1940 2,21 ,099 Jones Aug. 20, 194010 2,296,614 Hearne Sept. 22, 1942

